The Dynamic Interaction Between Eyewitnesses and Interviewers: TheImpact of Differences in Perspective on Memory Reports and
Interviewer Behavior
Amy Bradfield DouglassBates College
Neil BrewerFlinders University
Carolyn SemmlerUniversity of Adelaide
Lorena Bustamante and Alexa HileyBates College
Despite myriad possible differences in perspectives brought to an investigative interview by eyewitnessesand interviewers, little is known about how such differences might affect eyewitness memory reports orinterviewer behavior. Two experiments tested the impact of such differences in a dynamic interactionparadigm in which participants served as eyewitnesses and interviewers. In Experiment 1 (N � 38 pairs),reporting goals for eyewitnesses and interviewers were manipulated in a factorial design, with partici-pants instructed to provide or obtain either as much information as possible or only accurate information.Matching interviewer�interviewee instructions promoted accurate reporting, regardless of the actualcontent of the instructions. In Experiment 2 (N � 45 pairs), access to information about corroboratingeyewitness identifications was manipulated in a factorial design. Corroborating information affectedinterviewers, but not eyewitnesses. When interviewers did not have access to corroborating information,they provided more negative feedback, and there was a trend toward interrupting more and asking moreyes/no questions. These experiments indicate that differences in perspective can have effects on both thecontent of a witness’s report and the behavior of an interviewer. The potential for differences inperspective should be considered in research on protocols intended to maximize eyewitness reportaccuracy.
When investigating a crime, forensic interviewers rely on wit-nesses for information about how the crime unfolded, descriptionsof the culprit, and, often, identifying the culprit. This informationshapes the nascent investigation in important ways, sometimesdirecting it toward innocent suspects. For example, DNA exonereeJames Bain was first implicated because the victim’s description ofthe perpetrator “sounded like” him (Innocence Project, n.d.). Justas eyewitness reports can spontaneously misdirect an investiga-tion, police can collect erroneous information from eyewitnessesthrough flawed interview techniques. The recognition of howinterviewers can negatively affect the content of witness reports
has stimulated research on protocols designed to maximize eye-witness accuracy (e.g., the Cognitive Interview; Geiselman et al.,1984). Although these protocols have been responsible for signif-icant improvements in police interviewing methods, they ignorethe potential for preinterview differences in interviewer�inter-viewee perspective to alter either the eyewitness’s report or theinterviewer’s behavior.
In the current research, we examined differences in preinterviewgoals (Experiment 1) and access to evidence (Experiment 2).Differences in both goals and access to evidence are likely featuresof investigative interviews. For example, an interviewer might
Editor’s Note. Brian Cutler served as action editor for this article.—Margaret Bull Kovera
This article was published Online First May 6, 2013.Amy Bradfield Douglass, Lorena Bustamante, and Alexa Hiley, Depart-
ment of Psychology, Bates College; Neil Brewer, School of Psychology,Flinders University, Adelaide, Australia; Carolyn Semmler, School ofPsychology, University of Adelaide, Adelaide, Australia.
This research was supported by a National Science Foundation grant tothe first, second, and third authors (#0921193). Any opinions, findings, andconclusions or recommendations expressed in this material are those of the
authors and do not necessarily reflect the views of the National ScienceFoundation. The research was also supported by an Australian ResearchCouncil Discovery grant and an ARC Linkage International Social Sci-ences Collaboration grant.
Data from both experiments were presented at annual conference of theAmerican Psychology�Law Society, San Juan, Puerto Rico, in March2012. An earlier version of Experiment 1 was presented at the biennialconference of the Society for Applied Research in Memory and Cognition,New York, New York, in June 2011.
Correspondence concerning this article should be addressed to AmyBradfield Douglass, Department of Psychology, Bates College, 4 AndrewsRoad, Lewiston, ME 04240. E-mail: [email protected]
rush through instructions during a crime scene interview, failing toexplain that he or she wants all details recalled (i.e., the “reporteverything” component of the Cognitive Interview; Geiselman etal., 1984). Without that explicit guidance, an eyewitness mightreport only those details recalled with high confidence, potentiallyomitting crucial details from the report (cf. Yaniv & Foster, 1995).In terms of preinterview differences in access to evidence, inter-viewers typically have information unavailable to eyewitnesses(e.g., knowledge about another witness’s identification). In othercases, discussions between cowitnesses might mean that an eye-witness has information unavailable to an interviewer (cf. Skager-berg & Wright, 2008).
Differences in preinterview variables are important because theyhave the potential to create differences in how the eyewitness andthe interviewer approach the interview. At this point, we do notknow how any differences will affect the interviewer’s behaviorand/or the quality or quantity of details obtained from the eyewit-ness. To examine the effect of differences in preinterview variableson eyewitness reports and interviewer behavior, we created adynamic interview paradigm in which one of each pair of partic-ipants served as the interviewer and the other as the eyewitness.Before describing our experiments in detail, we briefly reviewrelevant literature.
Investigative Interviews
Eyewitness interviews often contain a number of undesirablepractices, such as asking leading or suggestive questions, inter-rupting witnesses, and discouraging witnesses from offering anyinformation not directly related to a given question (e.g., Snook &Keating, 2011). For example, although training cautions interview-ers against using closed questions, field studies have indicated thatinterviewers routinely violate this guideline, with as many as34.5% of questions classified as closed rather than open-ended(Snook & Keating, 2011; see also Clarke & Milne, 2001). Otherfield studies have shown that, on average, experienced interview-ers interrupt witnesses 7.5 s after an interview begins (Fisher,Geiselman, Raymond, Jurkevich, & Warhaftig, 1987). More re-cently, a sample of 26 experienced detectives ignored key featuresof effective interviewing, preferring closed questions to open ones,interrupting witnesses, and even insulting them during the courseof the interview (Schreiber Compo, Gregory, & Fisher, 2010).These practices decrease both the amount and the accuracy ofinformation provided by witnesses.
These undesirable practices occur in part because many profes-sional interviewers receive only brief training on how to conductinterviews with eyewitnesses (e.g., Snook, Eastwood, Stinson,Tedeschini, & House, 2010). When interviewers are trained, thepreferred protocol is the Cognitive Interview (Fisher & Geiselman,1992; Geiselman et al., 1984). This protocol instructs interviewersto guide witnesses through four processes: mental reinstatement ofcontext, the recall of the maximum possible amount of informa-tion, changing the order of narration, and retelling the scene froman alternative perspective (see Memon, Meissner, & Fraser, 2010,for a meta-analysis). Several decades of research have confirmedthat interviewers trained with the Cognitive Interview outperformuntrained interviewers, as measured by the amount of accurateinformation collected from witnesses (e.g., Memon et al., 2010).Even though the Cognitive Interview has clear benefits, some
trained interviewers fail to follow established protocols if time haselapsed since training (Smith, Powell, & Lum, 2009) or becausethey are not convinced that the techniques are effective (e.g.,Wells, Memon, & Penrod, 2006).
Experiment 1
Investigative interview protocols do not account for varyingexpectations that might be brought to an interview by eitherinterviewers or eyewitnesses. In our first experiment, we focusedon how differences in expectations can shape an investigativeinterview. Before describing specific predictions in the context ofan eyewitness interview, we briefly review relevant data on ex-pectations more broadly, all of which demonstrate the clear role ofexpectations in shaping behavior. First, at a basic social level,people who expect interaction partners to be sociable find evidenceto confirm that expectation in a brief conversation. Even morestriking is that independent observers actually rate the interactionpartners as more sociable (e.g., Snyder, Tanke, & Berscheid,1977). The same pattern appears in school settings where teacherswho expect students to “bloom” behave in such a way that thestudents actually outperform peers who are not expected to bloom(e.g., Rosenthal, 2006).
More directly related to psycholegal research, expectations alsoshape behavior in all phases of criminal investigations (e.g., seeFindley, 2012), particularly in response to confession evidence(e.g., Kassin, 2012). For example, interviewers led to believe in theguilt of a suspect select more guilt-presumptive questions than dointerviewers led to believe the suspect is innocent. Moreover, thesequestions actually produce more defensive behavior from suspects,as judged by independent observers (Kassin, Goldstein, &Savitsky, 2003). Even without the interpersonal demands of aninterrogation, expectations about the guilt of a suspect shapeevaluations of a witness’s identification. As an example, peopleevaluate witnesses more positively if the witness’s statement con-firms their suspicions of a suspect’s guilt than if it seems toexonerate the suspect (Ask & Granhag, 2007). Therefore, the veryreal possibility exists for interviewers to shape a witness’s reportbased on prior expectations (i.e., goals) that exist before an inter-view begins.
There are many scenarios in which interviewers and eyewit-nesses might have different goals for an interview. For example,suppose an interviewer fully embraces the Cognitive Interview buttruncates a witness’s report. Why might this happen? Imagine aninterviewer who interviews the last in a series of witnesses to thesame crime. By this point, the interviewer is likely to have devel-oped a schema for the crime and perhaps even harbor suspicionabout a specific suspect. The interviewer may, therefore, be moreinterested in details that confirm what has previously been col-lected than in fully plumbing the depths of the last witness’smemory. This tendency would be consistent with research in socialpsychology that has demonstrated the confirmation bias whereinpeople seek out information that supports their existing belief (e.g.,Nickerson, 1998) or distorts existing information to support a priorbelief (biased assimilation; e.g., Lord, Ross, & Lepper, 1979).
To examine the impact of differences in interviewer�inter-viewee goals, witnesses in the current research were either told (a)to provide only accurate information or (b) to provide as muchinformation as possible. Similarly, interviewers were either told (a)
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291INTERACTION BETWEEN EYEWITNESSES AND INTERVIEWERS
to collect only accurate information or (b) to collect as muchinformation as possible. We chose to focus on goals that eitheremphasized quantity or accuracy, because people are known totrade-off these factors against one another in their memory reportsin both general knowledge contexts (e.g., Koriat & Goldsmith,1994, 1996; Goldsmith, Koriat, & Weinberg-Eliezer, 2002) andeyewitness contexts (Weber & Brewer, 2008).
To measure the impact of our goal manipulation on witnessreports, we measured the grain size of details reported: whether awitness reports an item in very fine detail (e.g., he was wearing anavy blue V-necked sweater) or at a much coarser level (e.g., hewas wearing a dark-colored sweater). When confidence in anitem’s accuracy is high, witnesses tend to report fine levels ofdetail; when it is low, they are more likely to report coarse levelsof detail. When confidence is very low, witnesses are likely towithhold information (Goldsmith et al., 2002; Weber & Brewer,2008). Grain size is an important component of witness reports,and ignoring it can mask useful information. For example, somedata have indicated that witnesses produce equivalent accuracyacross retention intervals of different length (cf. Fisher, 1996); thispattern might be due to witnesses’ choice to produce a smallerproportion of fine-grain details in favor of coarse-grain details asretention intervals increase (Fisher, 1996; Goldsmith, Koriat, &Pansky, 2005; Weber & Brewer, 2008). To measure the impact ofgoals on interviewer behavior, we measured the number of wordsspoken, the type of questions asked, the amount of feedbackdelivered, and the type of feedback delivered; these variables aredescribed in detail in the Method section.
One possible outcome of manipulating goals is that eyewitnessand interviewer behavior will be driven by the extent to whichtheir respective instructions match, regardless of the actual contentof the instructions. This possibility is suggested by research inindustrial-organizational settings where clear understanding ofjob-specific duties (i.e., role clarity rather than role ambiguity,e.g., Kahn, Wolfe, Quinn, Snoek, & Rosenthal, 1964; Podsakoff,MacKenzie, & Fetter, 1993) makes “. . .completion of one’s dutieseasier as a result of expectations being more explicit” (Panaccio &Vandenberghe, 2011, p. 1460). To the extent that matching in-structions facilitate role clarity, witnesses should find it easier toprovide accurate information. Under this condition, eyewitnessesshould produce a higher volume of accurate information (bothfine- and coarse-grain details) because they can concentrate ontheir task, rather than being distracted by confusion over the goalsof the interview. For their part, interviewers should be less in-volved in the interview because they trust that the witness under-stands the goals of the interview and does not need to be remindedwith feedback or directive questions. That a subtle, unexpressedfeature of the interviewer�interviewee relationship might producemeasurable effects in memory reports, for example, is consistentwith research that has shown the influences from nonblind photo-spread administrators on identification choices and eyewitnessconfidence, even in the absence of explicit influence attempts (e.g.,Phillips, McAuliff, Kovera, & Cutler, 1999; Dysart, Lawson, &Rainey, 2012, respectively).
Alternatively, it is possible that eyewitness reports and inter-viewer behavior will be driven by the content of the instructionsrather than whether the instructions match. This might occur ifparticipants are attentive to the task, rather than the interactionbetween themselves and their interview partner. In this scenario,
when witnesses have quantity instructions (i.e., give or collect asmuch information as possible), they should produce a relativelylarge volume of both fine- and coarse-grain information, but over-all accuracy will be relatively low. But, as suggested by Goldsmithet al. (2002), even under quantity instructions, the precise outputpattern will depend on how interviewees balance the competingdemands for informativeness (i.e., maximizing the informationavailable in a statement that is achieved through fine-grain report-ing) and preserving accuracy (achieved by focusing on coarse-grain information). Natural tendencies to maximize informativenessor accuracy should result in biases toward fine- or coarse-grain re-porting, respectively. Under quantity instructions, interviewersshould probe for information by asking more questions (especiallyclosed questions) and providing more feedback so to encouragewitnesses to report anything they remember.
In contrast, when witnesses have accuracy instructions, theyshould produce abundant but predominantly coarse-grain detailsbecause this should ensure reasonable accuracy while producingacceptable output quantity. However, to the extent that interview-ees seek to be informative, it is also not out of the question thatthey will produce predominantly fine-grain details that are few innumber but high in overall accuracy, because interviewees aretrying to maximize informativeness while at the same time com-plying with the accuracy instruction (cf. Goldsmith et al., 2002).For interviewers, instructions that encourage accuracy might beexpected to produce directions to interviewees about the objectivesof the interview at the outset. When the interview is underway,however, the interviewer might be expected to play a relativelypassive role—apart from perhaps an occasional reminder aboutaccuracy—because they have no way of evaluating the accuracyof the interviewee’s responses.
Method
Design. The design was a 2 � 2 (Interviewer Goal [quantity,accuracy] � Eyewitness Goal [quantity, accuracy]) fully random-ized between-subjects factorial.
Participants. The data for this study were collected in twolocations, one large university in Australia (n � 17 pairs) and onesmall college in the United States (n � 21 pairs). Participants werecompensated $20 AUD or $10 USD for approximately 30 min oftheir time. Because there were no three-way interactions betweenlocation and our independent variables, location is not discussedfurther, Fs(1, 30) � 3.61, ps � .07, �2s � .11, widest 95%confidence interval (CI) for �2 [.00, .21].
Procedure. Two participants signed up for each 30-min timeslot. Before the experiment began, students were asked to confirmthat they did not know their partner. Participants were then ran-domly assigned to either the role of interviewer or witness bydrawing from among slips of paper with a role printed on them.The interviewer remained seated in the waiting area, and thewitness was escorted into the interview room. At this point, wit-nesses heard that the study was designed to examine “memoryrecall in eyewitness testimony.” They were randomly assigned tohear instructions to provide as much information as possible whendescribing the to-be-witnessed event (quantity condition) or toprovide only accurate information (accuracy condition). Instruc-tions were provide privately to each member of the pair. At thispoint, questions, if any, were answered about the content of the
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292 DOUGLASS, BREWER, SEMMLER, BUSTAMANTE, AND HILEY
instructions. The witness was then left alone to watch a stagedbank robbery video. This video was approximately 40 s long anddepicted two men robbing a bank before escaping in a car (Weber& Brewer, 2008). Each suspect’s face was clearly visible forseveral seconds in the video, as were those of the clerks andcustomers, as well as the getaway vehicle.
While the witness watched the video, the experimenter returnedto the waiting area to give the interviewers their instructions.Interviewers heard that the study was designed to examine theefficacy of different styles of police interviews and were instructedto either gather as much information as possible from their witness(quantity condition) or to elicit only accurate information (accu-racy condition). Interviewers were told that the video was of abank robbery, but received no further details and were not given aprescribed set of questions to ask. No mention was made to eitherthe witness or the interviewer of the fact that their partner mightreceive different instructions.
After the witness indicated that they had finished watching thebank robbery video, the interviewer was brought into the roomwhere participants were informed that the interview would bevideotaped so to provide an accurate transcript. Interviewers weregiven a sheet of paper to make notes of the witnesses’ responses,but were told not to provide a verbatim record of the interview,because it would be possible to refer to the video to resolve anyquestions that might arise. The experimenter then turned on thevideo camera and left the room. Participants were instructed toopen the door to the interview room when they were finished.
Once participants indicated that they had concluded the inter-view, the experimenter returned, shut off the video camera, col-lected the interviewer’s notes, and asked each participant to fill outa short questionnaire about their experience during the interview.1
After instructing participants not to discuss their answers with oneanother, the experimenter stepped into the hall while the partici-pants completed the questionnaires. Finally, participants werepaid, fully debriefed, and thanked for their participation.
Coding eyewitness reports. Each videotaped interview wastranscribed and each discrete piece of information was coded forgrain size (fine vs. coarse) and accuracy. For example, a witnesswho said that the culprits “got into a white old-looking car” wasscored as providing one fine-grain accurate detail for “white” andtwo coarse-grain accurate details for “car” and “old-looking.”Interviews were also coded for the number of words used by theinterviewer and witness. Each interview was coded by two inde-pendent coders, each of whom was blind to experimental condi-tion. Cronbach’s alpha was calculated for a subset of 22 interviews(mean Cronbach’s alpha � .97, range: .94�.99). Coding disagree-ments were resolved by discussion.
Coding interviewer behavior. Interviewers’ behaviors werecoded for positive/neutral feedback (e.g., “great, ok, good”), neg-ative feedback (e.g., “it sounded like you were kind of unsureabout a lot of things”), number of words used, and type of ques-tion. The type of question was categorized as either open (requir-ing a detailed response, e.g., “And, so what have you witnessed?”),closed (requiring a one or two word answer, e.g., “Did they haveany weapons at all?”), multiple (introducing multiple options intothe question, e.g., “Were [the robbers] normal sized or were theytall or short?”), and yes/no (requiring only a yes/no response, e.g.,“Do you think he was on drugs?”) (cf. Schreiber Compo et al.,2010). Interviewer behavior was coded by two coders, each of
whom was blind to experimental condition (Cronbach’s alpharange: .61�.92). Coding disagreements were resolved throughdiscussion.
Results
Eyewitness memory reports. Eyewitness reports producedfour dependent variables: number of coarse-grain accurate details,number of fine-grain accurate details, number of coarse-graininaccurate details, and number of fine-grain inaccurate details.Most of our dependent variables were correlated, with valuesexceeding r � .30. Therefore, we conducted a 2 � 2 (InterviewerInstructions � Eyewitness Instructions) multivariate analysis ofvariance (MANOVA). There were no main effects of either inde-pendent variable on eyewitness reports, Fs(4, 31) � 0.83, ps �.52, �2s � .10, widest 95% CI for �2 [.00, .22]. However, therewas a significant omnibus interaction between eyewitness andinterviewer instructions, F(4, 31) � 3.28, p � .02, �2 � .30, 95%CI for �2 [.002, .44].
To assess which variables were uniquely responsible forchanges in eyewitness memory reports, we used a stepdown anal-ysis of variance (ANOVA) procedure (Tabachnick & Fidell, 1989)on the four dependent variables listed above: accurate coarse-graindetails, accurate fine-grain details, inaccurate coarse-grain details,and inaccurate fine-grain details. To determine the order in whichthe dependent variables were entered into the stepdown procedure,we prioritized them as a function of the variance explained in thetotal number of fine- and coarse-grain details reported. Using aseries of simple linear regressions, the variables in descendingorder were: number of coarse-grain accurate details, number ofcoarse-grain inaccurate details, number of fine-grain inaccuratedetails, and number of fine-grain accurate details.
Once the prioritization of dependent variables was determined,each dependent variable was analyzed in a univariate two-wayANOVA with any higher priority dependent variables entered ascovariates. The stepdown analysis revealed a significant uniquecontribution of accurate coarse-grain details to the interactionbetween eyewitness and interviewer instructions (see Table 1 forresults from stepdown analysis). Eyewitness performance wassuperior when instructions matched compared with mismatched. Atwo-sample t test indicated that the average number of accuratecoarse-grain details was significantly higher when instructionsmatched (M � 26.89, SD � 5.43) compared with when they weremismatched (M � 19.50, SD � 6.33), t(36) � 3.84, p � .001, d �1.06, 95% CI for d [0.53, 1.92] (see Figure 1). No other dependentvariable provided a unique contribution to the interaction betweeneyewitness and interviewer instructions.
Interviewer behavior. Interviewer behavior was analyzedwith a 2 � 2 (Interviewer Instructions � Eyewitness Instructions)MANOVA using seven unique dependent variables: number ofyes/no questions, number of multiple choice questions, number ofleading questions, number of closed questions, number of openquestions, instances of positive feedback, and instances of negativefeedback. There were no significant multivariate main or interac-
1 Because the questionnaire data were not central to our research hy-potheses and for the sake of brevity, we have not reported those resultshere.
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293INTERACTION BETWEEN EYEWITNESSES AND INTERVIEWERS
In Experiment 1, we manipulated instructions for eyewitnessesand interviewers in a dynamic interview paradigm. For eyewit-nesses, we found that matching trumped content: the extent towhich instructions matched mattered more than what the instruc-tions actually were. Eyewitness performance was enhanced whentheir instructions matched their interviewer’s, as measured by thenumber of accurate coarse-grain details reported. The effect oneyewitnesses occurred despite the fact the videotaped interviewsrevealed that none of the pairs discussed their respective instruc-tions with one another. Therefore, any effect of matching instruc-tions was communicated through a mechanism more subtle thanexplicit confirmation of “being on the same page.” As noted in theintroductory section, one possible mechanism for these effects isrole clarity (e.g., Kahn et al., 1964), whereby understanding theinteraction goals makes the task easier to complete. Of note, theincreased accuracy produced by eyewitnesses resulted from inter-viewer�eyewitness pairs in which instructions matched on accu-racy or on quantity. That the matching of instructions was more
important in producing accurate eyewitness reports than the con-tent of instructions speaks to the role of the relationship betweeninterviewer and eyewitness.
If the relevant mechanism is role clarity, future research mightfind differences on questionnaire items assessing the extent towhich each person understands their role in the interview or howeasy it was to produce their reports. Similarly, if instructions arematched on the desire for fine-grain information or on the neces-sity to collect information on clothing, higher proportions of fine-grain or clothing-related information would be expected fromeyewitnesses compared with those who produce reports in condi-tions in which instructions mismatched.
The notion that role clarity is responsible for witnesses’ in-creased accurate coarse-grain details is consistent with a broadrange of motivational theories. At their most basic level, thesetheories argue that people’s behavior is shaped by the likelihood ofobtaining positive outcomes (e.g., Skinner, 1974). For example,some police officers have reported viewing shift choices as re-wards, suggesting that the presence of an opportunity to select adesirable shift might encourage positive workplace behavior(Johnson, 2009). In the current context, the positive outcome issimply gaining the interviewer’s approval and believing oneself tobe an effective witness. Future research directed at the precisefeatures of the relationship that encourage accurate reporting mightbe useful avenues to improve the outcome of witness interviews.
We found no effects of instructions on interviewer behavior.Regardless of the content of the instructions or the extent to whichthey matched their partner’s, interviewers behaved consistentlythroughout the interview. One explanation is that our interview-ers—just as in many real crime situations—had no way of eval-uating progress in relation to their goal. When instructed to collectonly accurate information, for example, interviewers could notassess whether the information provided was accurate. Similarly,when instructed to collect as much information as possible, inter-viewers had no way of knowing whether witnesses had moreinformation available to report. Another explanation is that ourmeasures were not appropriately designed to detect differences ofthis type in interviewer behavior. Future research incorporatingtargeted dependent measures and manipulating interviewers’ abil-ity to assess performance might indicate that interviewer behaviordoes vary as a function of goal or matching as long as there is anobjective standard against which to measure performance.
Table 1Stepdown Analysis for Eyewitness Reports in Experiment 1
Independent variable Dependent variable Univariate F df Step F df p
Figure 1. Significant interaction between eyewitness and interviewerinstructions on the number of accurate coarse-grain details reported inExperiment 1.
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294 DOUGLASS, BREWER, SEMMLER, BUSTAMANTE, AND HILEY
Experiment 2
Experiment 1 demonstrated the impact of different goals for aninvestigative interview on eyewitness reports through a simplemanipulation of instructions. Experiment 2 examined the effect ofdifferences in access to forensic evidence. As with differences ininstructions, the potential for differences in knowledge about ev-idence is clear. For example, interviewers might have access toevidence from analyses of the crime scene or conversations withother law enforcement officials; this information would be un-available to witnesses. Similarly, witnesses have information un-available to interviewers in the form of knowledge about the crime,perpetrator appearance, conversations with cowitnesses, and theirown behavior.
We elected to manipulate access to cowitness corroboration forthree reasons. First, cowitness conversations are common: In asample of 60 real witnesses in the United Kingdom, 88% reportedhaving at least one cowitness, and 58% of those individuals dis-cussed the crime with their cowitness (Skagerberg & Wright,2008; see also Paterson & Kemp, 2006). Second, cowitness infor-mation has powerful effects on identification decisions, memoryreports, and confidence. Hearing misinformation about a perpetra-tor’s appearance from a cowitness can undermine subsequentidentification accuracy (Zajac & Henderson, 2009). Hearing acowitness describe an event can affect memory reports (e.g.,Wright, Self, & Justice, 2000); hearing details about an event froma cowitness can affect recall, especially when the details areunseen by the witness (e.g., Hope, Ost, Gabbert, Healey, & Len-ton, 2008). Additionally, hearing about a cowitness’s identificationdecision can dramatically inflate or deflate a witness’s own con-fidence, depending on whether the cowitness corroborates or con-tradicts one’s own identification, respectively (Luus & Wells,1994).
Finally, although there are no data specifically suggesting thatcowitness information affects interviewers, several related lines ofresearch support the potential for these effects. The first is thatinvestigators’ beliefs are malleable as a function of whether wit-nesses confirm their hypothesis about the identity of the suspect(e.g., Dahl, Lindsay, & Brimacombe, 2006). In one experiment,investigators who learned that their witness identified the suspectasked more leading questions than did investigators who learnednothing about their witness’s accuracy (MacLean, Brimacombe,Allison, Dahl, & Kadlec, 2011). Additionally, as described earlier,investigators are susceptible to the confirmation bias. Most exam-inations of this effect have measured investigators’ evaluations ofa suspect, rather than of a witness (e.g., Ask & Granhag, 2007).However, evidence that a cowitness identified the same person asthe to-be-interviewed witness might have parallel effects in that itencourages interviewers to confirm their preexisting hypothesisthat the witness has an accurate recall of the event.
To examine whether evidence about cowitness identificationsaffects an interview, we manipulated access to this evidence, asdescribed below. We expected to find main effects of corroborat-ing identifications on both eyewitness memory reports and inter-viewer behavior. For eyewitnesses, we expected that corroborationof their identification would increase their confidence in theirmemory of the event, thereby raising their reporting criterion.These witnesses should report fewer fine-grain details and fewertotal details, because fewer details exceed the confidence threshold
for reporting. In addition, the proportion of fine-grain (vs. coarse-grain) details should decrease.
Partial evidence for this criterion shift would come from in-creases in witnesses’ confidence as a function of hearing aboutcorroborating evidence. Evidence for this possibility comesfrom criterion shifts in other research paradigms. For example, inthe context of people attempting to recall words from a studied list,shifting the reporting criterion has been accomplished by manip-ulating study time: people who have studied a list extensivelyexpect to have a stronger memory than those who have studied itless. As a result, they set a stricter criterion for reporting a wordbecause they expect the target stimulus (if previously seen) to behighly familiar (Morrell, Gaitan, & Wixted, 2002; Stretch &Wixted, 1998). Because we have no published research specifi-cally addressing the impact of corroborated identifications oneyewitness memory reports, this prediction is necessarily tentative.For interviewers, we expected that corroboration of the eyewit-ness’s identification would elevate the interviewer’s confidence inthe witness’s memory, encouraging the interviewer to rely on thewitness to produce the best information, rather than having tosolicit the information through detailed questions or repeated feed-back. This should be reflected in fewer questions, fewer interrup-tions, and fewer words from the interviewer.
Method
Design. The study was a 2 � 2 (Interviewer Knowledge ofCorroborating Information [yes, no] � Eyewitness Knowledge ofCorroborating Information [yes, no]) fully randomized between-subjects factorial design.
Participants. Participants (N � 45 pairs) were undergraduatestudents from a small college in the United States. Participantswere recruited through Facebook groups, e-mail, and word-of-mouth. They received $10 USD for their participation. Of the 90participants, 56 (62%) were women (55% of eyewitnesses werewomen; 69% of interviewers were women). In 55% of the pairs,participants were of the same sex. Because of the low sample sizefor each sex combination, this variable is not analyzed further.
Procedure. As in Experiment 1, two participants were sched-uled for each 30-min time slot, and participants were not allowedto sign up with a friend or acquaintance. Participants were ran-domly assigned to their roles using the methodology described inExperiment 1.
Eyewitness procedure. Eyewitnesses remained in the labora-tory room and watched a mock crime video of several individualsrobbing a storage unit. Each individual is in view for approxi-mately 120 s, with a clear view of each culprit for approximately15–20 s (see Charman & Wells, 2007, for a detailed description ofthe video).
After the video was over, biased instructions were used toensure that all eyewitnesses made an identification (cf. Malpass &Devine, 1981). In addition, because we did not want the corrobo-ration manipulation to be confounded with identification accuracy,we used a target-absent lineup to ensure that any identificationmade was false. After the identification, eyewitnesses indicatedhow confident they were in their identification on a scale from 0%(not at all confident) to 100% (extremely confident). After provid-ing their confidence rating, half of the participants heard nothingfurther about the accuracy of their identification or the extent to
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295INTERACTION BETWEEN EYEWITNESSES AND INTERVIEWERS
which others made the same identification. The other half receivedcorroborating information based on the manipulation used in Sem-mler, Brewer, and Wells (2004):
Wow, this is very interesting! My professor used the same lineupduring the summer and 84 out of 87 participants selected the sameperson as you did!
The experimenter then left the laboratory to retrieve the inter-viewer.
Interviewer procedure. While the eyewitness was watchingthe crime video, the interviewer was in the hallway reviewing afictitious police report containing basic crime details (e.g., loca-tion, date, time). When the experimenter returned to the inter-viewer, the experimental manipulation was delivered. Half heardnothing about corroborating cowitness identifications. The otherhalf heard a version of the manipulation provided to witnesses:
Wow, this is very interesting! My professor used the same lineupduring the summer and 84 out of 87 participants selected the sameperson as the eyewitness!
Each participant was asked to refrain from sharing the corrob-oration information with their partner. This instruction ensured thatasymmetrical access to evidence was held constant during theinterview, where relevant.
Interview. Interviewers then returned to the laboratory to poseas many questions as they deemed necessary to figure out whathappened. Eyewitnesses received no instructions prior to the in-terview. The experimenter then exited the room, leaving the par-ticipants to conduct a simulated investigative session. All interac-tions between interviewers and eyewitnesses were videotaped.After 7 min of interaction (which Experiment 1 indicated was thetypical upper boundary for meaningful interaction), the experi-menter interrupted the session. Participants then completed apostinterview questionnaire.
Postinterview questionnaire. After the interview, eyewit-nesses rated their confidence in the accuracy of the memory reportthey had just provided using the same scale as used before theinterview. Using a series of 10-point scales, they also indicated theextent to which they believed they provided highly detailed infor-mation (1 � I provided mostly broad information and 10 � Iprovided mostly detailed information), how often the interviewerinterrupted them (1 � the investigator never interrupted me and10 � the investigator frequently interrupted me), how often theinterviewer let them know how they were doing (1 � the investi-gator never let me know how I was doing and 10 � the investigatorfrequently let me know how I was doing), and the type of com-ments they received (1 � I received mostly negative comments and10 � I received mostly positive comments).
Interviewers also completed a questionnaire in which they ratedthe eyewitness and themselves on six questions: how confidentthey were in the accuracy of the eyewitness’s identification, howconfident they were in the accuracy of the eyewitness’s memoryreport (both questions used a scale from 0�100%), the extent towhich they thought the eyewitness provided detailed information(1 � the eyewitness provided mostly broad information and 10 �the eyewitness provided mostly detailed information), how oftenthey interrupted the witness (1 � I never interrupted the witnessand 10 � I frequently interrupted the witness), how often they let
the witness know how he or she was doing (1 � I never let thewitness know how he or she was doing and 10 � I frequently letthe witness know how he or she was doing), and the type offeedback delivered to the witness (1 � I gave mostly negativecomments and 10 � I gave mostly positive comments).
Interview coding. Eyewitness reports and interviewer behav-ior were coded using the same scheme developed for Experiment1. As in Experiment 1, each interview was coded independently bytwo coders, each of whom was blind to condition (mean Cron-bach’s alpha � .95, range: .82�.99). Coding disagreements wereresolved through discussion.
Results
Corroboration manipulation check. A subset of witnesses(n � 20) completed a manipulation check question asking whetherthey recalled the corroboration information. Of these witnesses,90% accurately recalled the manipulation.
Eyewitness memory reports. Eyewitness reports were codedfor accuracy, grain size, and proportion accurate. These variableswere analyzed with a 2 � 2 (Interviewer Knowledge of Corrob-orating Information [yes, no] � Eyewitness Knowledge of Cor-roborating Information [yes, no]) MANOVA on the four uniquevariables of accurate course-grain details, inaccurate coarse-graindetails, accurate fine-grain details, and inaccurate fine-grain de-tails. There were no significant effects on eyewitness reports, Fs(4,38) � 1.36, ps � .27, �2s � .13, widest 95% CI for �2 [.00, .18].
Eyewitness self-reports. Eyewitness self-reports were ana-lyzed using a series of 2 � 2 univariate ANOVAs. There was atrend for eyewitnesses to report more frequent feedback frominterviewers who did not have corroborating information (M �2.91, SD � 2.04) compared with interviewers who did have thatinformation (M � 1.91, SD � 1.38), F(1, 41) � 3.67, p � .061,�2 � .08, 95% CI for �2 [.00, .25]. There were no significanteffects on any of the other eyewitness self-report variables, Fs(1,41) � 2.44, ps � .13, �2s � .06, widest 95% CI for �2 [.00, .22].
Interviewer behavior. Interviewer behavior was analyzedwith a 2 � 2 (Interviewer Knowledge of Corroborating Informa-tion [yes, no] � Eyewitness Knowledge of Corroborating Infor-mation [yes, no]) MANOVA on seven unique dependent variables:number of multiple part questions, number of yes/no questions,number of open questions, number of closed questions, instancesof positive feedback, instances of negative feedback, and thenumber of times the interviewer interrupted the eyewitness. Therewas a significant multivariate main effect of interviewer knowl-edge, F(7, 35) � 2.37, p � .04, �2 � .32, 95% CI for �2 [.00, .41].No other multivariate effects were significant, Fs(7, 35) � 1.39,ps � .24, �2s � .21, widest 95% CI for �2 [.00, .30].
As in Experiment 1, we conducted a stepdown analysis todetermine which variables uniquely contributed to the main effectof interviewer access to corroborating identification information(Tabachnick & Fidell, 1989). Using interviewers’ total words asthe global dependent variable, we conducted a series of simplelinear regressions to determine the prioritization for dependentvariables in the stepdown analysis. In descending order, the vari-ables were: number of yes/no questions, number of closed ques-tions, number of interruptions, negative feedback, number of mul-tiple part questions, positive feedback, and number of openquestions. The stepdown ANOVA revealed a significant main
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296 DOUGLASS, BREWER, SEMMLER, BUSTAMANTE, AND HILEY
effect of interviewer access to corroborating identification infor-mation on the amount of negative feedback interviewers delivered.Nonsignificant trends appeared on the number of interruptionsfrom interviewers and the number of yes/no questions used (seeTable 2 for results from stepdown analysis). In all cases, inter-viewers who had access to corroborating identification informationwere less involved in the interview than were interviewers who didnot have corroborating information (see Table 3 for descriptivestatistics).
Interviewer evaluations of eyewitnesses. There was one sig-nificant main effect on interviewers’ ratings of witnesses: inter-viewers reported higher confidence in the accuracy of eyewit-nesses’ identifications if they had access to corroboratinginformation (M � 6.91, SD � 1.23) versus when they did not havethat information (M � 5.35, SD � 2.46), F(1, 41) � 7.01, p � .01,�2 � .15, 95% CI for �2 [.001, .33]. Consistent with this patternwas a nonsignificant trend for interviewers to be more confident inthe accuracy of witnesses’ reports if they had access to corrobo-rating information (M � 7.05, SD � 1.62) versus when they didnot have that information (M � 6.00, SD � 2.20), F(1, 41) � 3.19,p � .081, �2 � .07, 95% CI for �2 [.00, .24]. There were no othersignificant effects on interviewers’ ratings of witnesses, Fs(1,41) � 2.65, ps � .11, �2s � .06, widest 95% CI for �2 [.00,.22].
Discussion
In this experiment, we manipulated interviewers’ and eyewit-nesses’ access to information about corroborating eyewitness iden-tifications. These manipulations had a direct effect on interview-ers. When corroborating information was not available tointerviewers, they gave more negative feedback; there was a ten-dency to interrupt more and ask more yes/no questions. Thiscollection of effects suggests two possible interpretations on thepart of interviewers. On the one hand, it is possible that corrobo-
ration suggested to the interviewers that the witness’s overallmemory was quite good, which would allow them to take a lessactive role during the interview, because they felt they could trustthe witness to produce an accurate report without assistance. Thisis supported by the finding that interviewers who had corroborat-ing information were more confident in the accuracy of the eye-witness’s identification and slightly more confident in the accuracyof the witness’s memory report. On the other hand, it is possiblethat interviewers with corroborating information were less in-volved in the interview because they felt that a detailed memoryreport of the crime was unnecessary in light of a well-supportedidentification.
Eyewitness memory reports were not directly affected bythe manipulation of corroborating identification evidence. Forthe confidence dependent measure, this result is attributableto the fact that eyewitnesses provided two confidence judg-ments: one before the corroboration manipulation was admin-istered and one after. That an initial confidence judgmentinoculated witnesses against subsequent inflation is consistentwith research on the postidentification feedback effect in whichprior thought about confidence mitigates the effect of feedback(e.g., Wells & Bradfield, 1999). As for the null effects on other
Table 3Adjusted Means (and Standard Errors) for Effects of InterviewerAccess to Corroborating Identification Evidence in Experiment 2
Dependent variables
Interviewer access tocorroborating identification
evidence
Yes No
Amount of negative feedback 3.89 (1.10) 7.18 (1.07)Number of interruptions 4.40 (0.77) 6.46 (0.75)Number of yes/no questions 10.96 (1.46) 14.40 (1.43)
Table 2Stepdown Analysis for Interviewer Behavior in Experiment 2
Independent variable Dependent variable Univariate F df Step F df p
297INTERACTION BETWEEN EYEWITNESSES AND INTERVIEWERS
measures, two possible explanations emerge. One is that ob-serving a criterion shift requires confidence judgments to shift(cf. Weber & Brewer, 2008). Because we found no differencesin witnesses’ confidence as a function of identification corrob-oration, a definitive assessment of whether the witnesses’ cri-terion did shift was not possible. Alternatively, it is possiblethat the inoculation observed on confidence judgments extendsto memory report measures as well. Extant data do not speak tothis exact question; postidentification feedback manipulationshave not yet been tested on the grain size of report details.
General Discussion
The two experiments presented here extend our understandingof investigative interviews by showing the impact of preinterviewdifferences on both eyewitness reports and interviewer behavior.In Experiment 1, matching instructions improved eyewitnessmemory reports, but did not change interviewer behavior. InExperiment 2, evidence about corroborating identifications re-duced interviewers’ involvement in the interview, but had no effecton eyewitnesses’ memory reports.
The effects presented in these two experiments demonstrate thecritical role of preinterview differences in perspective. For exam-ple, when eyewitnesses and interviewers approach an interviewwith different goals, the results are startling. More than sevenfewer accurate coarse-grain accurate details were obtained, a 27%decrease in the number of accurate coarse-grain details comparedwith a condition in which instructions matched. This result oc-curred even though the instruction manipulation was casuallydelivered and not highly specific. The omitted details could haveserious implications for a police investigation. Indeed, most persondescriptions are scant, averaging less than 10 characteristics (e.g.,Sporer, 1992; see Meissner, Sporer, & Schooler, 2007, for areview). Losing any of those accurate details substantially impairsthe police’s ability to locate the perpetrator. Simply knowing thata getaway automobile was light-colored might represent a key bitof information when combined with information about the culpritfrom other sources.
In addition to shaping the investigation by affecting the numberof accurate details reported, the current research shows that dif-ferences in perspective derived from access to evidence also haveimportant implications for an interviewer’s behavior. This is nicelydemonstrated by Experiment 2, in which lack of evidenceprompted interviewers to be more active. This finding is particu-larly suggestive because the manipulation tested here representsonly one of the myriad ways for eyewitnesses and interviewers toarrive at an interview with different knowledge about evidence. Ata minimum, interviewers will have knowledge about the extent towhich corroborating evidence exists (or does not), and eyewit-nesses will have privileged knowledge about the crime. Futureresearch manipulating access to DNA or other forensic evidencemight even show that an active interviewer increases witnesses’willingness to attempt an identification following the interview.Would this influence extend to the actual identification choice,making a mistaken identification more likely after an eyewitnessinteracts with an “active” interviewer? If so, the need to mitigateinterviewers’ influence on eyewitnesses becomes even more press-ing.
The observed differences in Experiment 1 are unequivocal im-provements in eyewitness reports. However, we hesitate to cate-gorically claim that matching instructions will always produceenhanced reports. For example, would interviewer�eyewitnesspairs whose instructions both emphasized guessing produce im-provements in the accuracy of eyewitness reports? In Experiment2, interviewers’ knowledge reduced their involvement in the in-terview, a change that is consistent with recommended interviewprotocols (e.g., Geiselman et al., 1984). This operationalization ofdifferences in perspective was neutral in terms of producing im-provements in eyewitness reports. Because we only tested onemanipulation of differences in access to forensic evidence, we arenot yet willing to offer a definitive assessment of whether accessto forensic information will always produce more desirable behav-iors. For both experiments reported here, varying the operational-ization of differences in perspective will be necessary before adecisive conclusion can be drawn about the positive versus nega-tive impact of differences in perspective.
One interesting direction for future research concerns the useof schemas and scripts on the part of the interviewer rather thanon the witness (cf. Mortimer, 1993). Although a number ofstudies have examined how a witness’s knowledge of crime-relevant schemas can affect their memories of the witnessedevent (e.g., García-Bajos & Migueles, 2003; Greenberg, West-cott, & Bailey, 1998; Tuckey & Brewer, 2003a, 2003b), therehas been no research that examines how an interviewer’s fa-miliarity with the same schema might affect the way in whichthe interview is conducted. In Experiment 1, anecdotal evidencefor this possibility comes from interviewers’ questions aboutweapons. Witnesses who watched the bank robbery video inExperiment 1 never actually saw a weapon, though weaponpresence was implied by the perpetrators’ body language. Inreporting on the presence of a weapon, witnesses fell into threecategories: incorrectly reporting having seen a weapon (aschema-consistent error), tentatively suggesting that it lookedlike the two men were armed but they had not actually seen agun, or simply indicating that there had been no weapons.Interviewers whose witnesses fell into the first category tendedto simply note the information and move on with the interview.Interviewers whose witnesses fell in the latter two categories,however, often expressed surprise and asked several follow-upquestions. After hearing a deliberately cautious, equivocalstatement, some interviewers replied with the following: “So hehad a gun, then.” One or two witnesses remained firm in theirambiguity by reiterating that it was only suggested that the menwere armed, but the majority of witnesses in this situationacquiesced to this drastic alteration without argument. Oneinterviewer was so perturbed by the equivocation that he saidwith blatant skepticism, “So you’re telling me that they justwalked in and demanded the money without showing anyweapons . . . and the lady just gave it to them?” Such an openlynegative reaction might easily intimidate a timid or compliantwitness into revising what was an accurate initial statement and,further, discourage them from reporting schema-incongruentdetails in the future.
Given the previous research on the role of schemas in eyewit-ness memory, witnesses’ tendency to include this inaccurate butschema-consistent information in their report is unsurprising. Whatis of greater interest is the extent to which interviewers’ reliance on
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298 DOUGLASS, BREWER, SEMMLER, BUSTAMANTE, AND HILEY
schemas might influence witness reports. Further research intohow schemas might affect questioning and how such questioningmight in turn affect witness memory would be useful in determin-ing exactly how and to what extent this occurs. One study hasdemonstrated that witnesses’ false memories for high-typicalityactions persisted even in the face of explicit warnings of thepotential for such errors (García-Bajos & Migueles, 2003). Itwould be worthwhile to explore whether such warnings might bemore efficacious in modifying the behavior of the interviewers.Because warnings aimed at the interviewer would not have tocompete with false memories, it seems possible that such inter-ventions might be at least somewhat more successful in curbingsuch behavior.
An important step for future research is to test how thesewitnesses and interviewers are evaluated by naive observers. Forexample, recent research has demonstrated the stark contrast inevaluations of an initial eyewitness confidence statement as afunction of whether it is read by the witness at trial or seen on avideotape of the actual identification procedure. In that research,when confidence inflated between the initial identification proce-dure and the trial, ratings of the defendant’s guilt were reduced, butonly when people saw the videotaped identification procedure, notwhen they merely heard the witness read a prior statement signi-fying low initial confidence (Douglass & Jones, 2013). In thecurrent research, recall that witness performance in Experiment 1was superior when instructions matched. Will that enhanced per-formance translate into more positive evaluations of the witnessand evaluations of the interviewers as placing less pressure on thewitness? In Experiment 2, interviewers provided more negativefeedback when they did not have information about corroboratingidentifications. Will witnesses whose interviewers provided morenegative feedback be evaluated as less accurate, even though theirobjective accuracy is comparable to witnesses whose interviewersdid not provide as much negative feedback? To answer suchquestions, showing the videotaped interviews to naive observers iscritical.
Another exciting possibility for future research is to examine theimpact of the manipulations tested here on interviewers’ memo-ries. According to one study, interviewers who use the CognitiveInterview, compared with a structured interview, produce signifi-cantly more accurate details when reporting what the witness said(Köhnken, Thürer, & Zoberbier, 1994). In Experiment 2, inter-viewers were more involved in the interview when they did nothave corroborating information. Would this involvement translateto better memory for the witness’s report details than when inter-viewers did not have corroborating information available? Or,would the involvement displayed by these interviewers disrupttheir ability to form complete memories of what the witnessreported?
One potential limitation of our experiments is that we did notuse “specialist” interviewers. However, there are two factors thatlead us to conclude that this may not be a serious limitation. First,the percentage of words spoken by our interviewers was remark-ably consistent with what is found for professional police inter-viewers. One study of 90 police interviews in Canada found that anaverage of 36% of the words spoken were by interviewers (Snook& Keating, 2011). For our data, the comparable values were 34%in Experiment 1 and 36% in Experiment 2. Second, most policeofficers receive little or no training on how to interview witnesses,
suggesting that, at least in terms of detailed training in how toconduct interviews, the police might not be entirely unlike ourresearch participants (e.g., Snook et al., 2010).
Implications
These data reinforce the social nature of information gatheringin a forensic context. In Experiment 1, accurate information wasincreased when witnesses’ and interviewers’ instructions matched,lending yet more support to Bartlett’s (1932) classic claim that“. . . memory appears to be directly influenced by social facts” (p.247). In Experiment 2, the interviewer’s lack of knowledge aboutcorroborating identifications increased involvement in the inter-view. Even though accurate recollection can be increased in somesocial combinations (e.g., matching instructions in Experiment 1),the likelihood of recreating that precise experimental condition inthe field is quite limited. Therefore, where possible, recall toolsthat eliminate or reduce the social aspect of remembering, suchas the Self-Administered Interview (e.g., Gabbert, Hope, & Fisher,2009), eye closure (e.g., Perfect et al., 2008), or blind procedures,where possible (e.g., Dysart et al., 2012; Phillips et al., 1999),should be advanced. In refining these protocols, psychologicalscientists should be vigilant for scenarios in which differences inperspective can emerge. Studies like the ones reported here willplay an essential role in developing our understanding of thesescenarios and their potential effect on eyewitness memory reportsand interviewer behavior, allowing us to more completely assessthe factors that shape investigative interviews.
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Received November 15, 2012Revision received February 18, 2013
Accepted February 21, 2013 �
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301INTERACTION BETWEEN EYEWITNESSES AND INTERVIEWERS
